1. Field of the Invention
The invention relates to a grinding machine and grinding method that grind an outer peripheral surface of a solid cylindrical or hollow cylindrical workpiece.
2. Description of the Related Art
In an prior art, in order to accurately grind an outer peripheral surface of a solid cylindrical or hollow cylindrical workpiece, for example, Japanese Patent Application Publication No. 62-282865 (JP-A-62-282865) uses a grinding machine equipped with a sizing device. The sizing device described in JP-A-62-282865, or the like, is used to determine a change timing at which the process is changed from rough grinding into finish grinding and a change timing at which the process is changed from finish grinding into spark-out. Specifically, the sizing device outputs a signal at the time when the outside diameter of a workpiece measured by the sizing device reaches predetermined outside diameters at the respective change timings, and the process is changed into the next grinding on the basis of the signal output from the sizing device.
However, the sizing device outputs a signal when the minimum diameter of a workpiece reaches a predetermined outside diameter. Therefore, if the radially cross-sectional shape of a workpiece is formed not in a perfect round shape but in an elliptical shape, there is a case where the minor axis of the workpiece has reached a predetermined outside diameter but the major axis has not yet reached the predetermined diameter. Various factors, such as fluctuations in grinding resistance may cause a workpiece to be machined into such an elliptical shape. Thus, after grinding, it is necessary to check the outer peripheral shape of a workpiece by an out-of-roundness measuring device. For example, an outer peripheral surface shape of a workpiece with respect to the rotation center of the workpiece, that is, whether a workpiece is decentered, the out of roundness of a workpiece, the surface texture of a workpiece, and the like, are checked as the outer peripheral surface shape of a workpiece.
In this way, when a workpiece is determined as a defective piece through checking after grinding, the workpiece cannot be shipped as a product. Furthermore, because of the checking process, a cycle time from the start of machining a workpiece to the completion of the workpiece extends. Then, cost increases because of the checking process.